Electromagnetic relays



May 4, 1965 w. H. D. YULE ELECTROMAGNETIC RELAYS 4 Sheets-Sheet 1 FiledApril 9, 1962 .lll I l l l I l l I I I l I l I I l I I I l l I I l I I lI IQIAII) \|||\\i|| llllllll 4 4. f \Lll' N I II III! III. l

Inventor WILLIAM H- a. raw

A Home y W. H. D. YULE ELECTROMAGNETIC RELAYS May 4, 1965 Filed April 9,1962 4 Sheets-Sheet 2 III/III I nvenlor W/LL/AM M D. Yl/Lf y 2 MAttorney y 4, 1965 I w. H. D. YULE 3,182,232

ELECTROMAGNETI C RELAYS Filed April 9, 1962 4 Sheets-Sheet 3 lnvenlorWILL/AM H. D- YULE Bywgf;

A Home y ELECTROMAGNETIC RELAYS Filed April 9, 1962 4 Sheets-Sheet 4 vInventor WILL/AM h. 0. YULE Attorney United States Patent 3,182,232ELECTROMAGNETIC RELAYS William Henry Drury Yule, London, England,assignor to International Standard Electric Corporation, New York, N.Y.,a corporation of Delaware Filed Apr. 9, 1962, Ser. No. 186,100 Claimspriority, application Great Britain, June 12, 1961, 21,134/ 61 6 Claims.(Cl. 317-471) This invention relates to electromagnetic relays and inparticular to means for reducing contact bounce, or chatter, in suchrelays.

According to the invention there is provided an electromagnetic relay inwhich contact bounce is reduced by providing permanent magnetic meansfor holding back the armature of the relay in the unoperated position,the armature being primarily biased back by other means.

An embodiment of the invention as applied to a nonpolarizedlight-current electromagnetic relay of the balanced armature type willhereinafter be described with reference to the accompanying drawings, inwhich:

FIG. 1 is a side elevation of the relay, sectioned through a sealingcover,

FIG. 2 is a left hand end elevation of FIG. 1, sectioned through thecover.

FIG. 3 is a part sectional end elevation along the line AA' of FIG. 1,

FIG. 4 is a partly sectioned plan view of the armature and movablecontact springs assembly.

FIG. 5 shows schematically the main magnetic circuit and arrangement ofthe armature and stationary contacts;

FIGS. 6, 7, and 8 show the plan view, right hand end elevation, and sideelevation respectively of a magnetic backstop for the relay.

The problem of contact bounce is general to electromagnetic relays. Ithas been found to be particularly acute when caused by the resonance ofa critically balanced relay armature. Such a relay is described inBritish Patent No. 811,262, and our invention will be illustrated asapplied to this relay.

Referring to FIGS. 1 and 2, the relay is enclosed in a metal cover 1soldered to a stamped metal base 2 and in known manner subsequentlysealed to avoid adverse effects of humidity and low air pressure on therelay.

The main magnetic circuit includes a bar-shaped core 3 of rectangularcross section and centrally recessed at each end. In the left-handrecess is attached a rightangled or L-shaped pole-piece 4, and in theright-hand recess is attached a right-angled or L-shaped polepiece 5,the polepieces 4 and 5 facing inwardly and being of different lengths.

Also attached in the right hand recess is a right-angled or L-shapednon-magnetic supporting piece 6. The portions of the longer polepiece 4and of the supporting piece 6 parallel to and spaced from the core 3 arerigidly attached to the base 2 by non-magnetic screws or studs 7 and 8respectively, so that resonant vibration of the assembly is reduced to aminimum.

Alternatively the supporting piece 6 may extend along the whole of thebase 2, with the longer polepiece 4 resting on the support piece 6 andthe screw 7 passing through both the polepiece 4 and the support 6.

Referring now to FIGS. 1, 6, 7 and 8 together, the magnetic backstop 28is positioned in the angle of the supporting piece 6. The view of themagnetic backstop 28 shown in FIG. 1 corresponds to that shown in FIG.8, and the line B-B on FIG. 7 corresponds to the width of the Supportingpiece 6.

The magnetic backstop 28 consists of a block of magnetic iron 29 inwhich are set two small permanent mag- 3,182,232 Patented May 4, 1965ICC nets 30. The magnets 36 are made of the material known by theregistered trademark Platinax.

The screw 8 passes through the base 2, the supporting piece 6, and intothe threaded hole 31 in the magnetic backstop 28, thus securing themagnetic backstop 28 in position.

Referring back, now to FIGS. 1 and 2 only, a Winding 9 may be wounddirectly onto the core 3, or prewound on a spool which is then slippedonto the core 3. External electrical connections for the winding 9 areprovided by connecting, as by soldering, the ends 10 of the winding 9 toseparate terminating pins 11 sealed through and insulated from the base2.

A flat armature 12 is pivoted about its central transverse axis on apivot pin 13 between supports 14 formed by bent-up side extensions atthe end of the longer polepiece 4. Alternatively, the armature supportsmay be bent down from side extensions at the end of the shorterpolepiece 5. The pin 13 is slightly bowed before insertion so that itholds itself in position after insertion through the armature and itssupports.

The armature 12 thus lies in a plane substantially parallel to the base2, inside the longer polepiece 4 and outside the shorter polepiece 5.

The main magnetic flux path is along the longer polepiece 4, thearmature supports 14, the pivot pin 13, the armature 12 and the shorterpolepiece 5. There is negligible flux leakage across the relativelylarge air gap between the polepiece 4 and the armature 12.

Thus, as shown in FIG. 5, the main magnetic circuit is in the shape of aC with its free ends oil-set in two spaced parallel planes and thecentrally pivoted armature 12 in a parallel plane intermediate the twospaced planes.

To prevent sticking between the sides of the armature and the innersides of the armature supports where relative movement occurs onoperation of the relay, washers 15 of non-magnetic material, e.g.,nickel silver, may be inserted therebetween.

The relay is provided with two sets of changeover contacts. As shown inFIGS. 3 and 4, two movable contact springs 16 are rigidly attached tothe top face of the armature 12 by screws 17, or by rivets, and aresandwiched between insulating blocks 18 and 19 so as to be insulatedfrom the armature 12 and from each other. The screws 17 bear on a clampplate 20. Thus it will be seen that the armature and moving contactassembly is substantially symmetrical about the central pivot of thearmature.

FIG. 4 is sectioned so as to clearly indicate the shape of the contactsprings 16. At each end of the portion of the springs 16 which areattached to the armature 12, extension pieces 21 are bent up and locatein a corresponding recess in the insulating block 19, thus preventingany longitudinal movement of the contact springs 16.

Semi-circular recesses 22 in the inner edge of the contact springs 16allow clearance for the shank of the screws 17, or rivets if used.

Returning to FIGS. 1 and 2, stationary contacts for co-operation withthe movable contact springs 16 are provided by terminating pins 23sealed through and insulated from the base 2, and made from contactmaterial or capped at one end with suitable contact metal to form thestationary contacts 24.

The movable contact springs 16 may be bent down in the form shown inFIG. 1 or alternatively may be straight, in which case the terminatingpins 23 must be extended upwards.

The resilience of the springs 16 is chosen to give satisfactory contactpressure and freedom from excessive bounce. In a miniature relay noseparate contacts are provided on the springs 16 which are themselvesmade ansaaea 3 of a suitable resilient contact material. Separatecontacts may of course, be provided if required.

In the unoperated position, the right hand (FIG. 1) contacts are closed,and the armature 12 is urged away from the shorter polepiece 5 bysuitably formed restoring springs 25', each attached at one end to aterminating pin 26 sealed through and insulated from the base 2, andeach attached at the other end to an angled extension piece 27 of amovable contact spring 16 at the centre of the armatrue 12.

The restoring springs 25 are made of a suitable resilient conductingmaterial, such as Phosphor bronze, and thus function in addition aselectrical connecting means to the movable contact springs 16.

As stated in the above description the armature 12 is biased back in theunoperated position by the restoring springs 25, and the resilience ofthe contact springs 16 is chosen to give freedom from excessive contactbounce. These two features were present in the earlier disclosed relaydisclosed in British Patent No. 811,262. In this embodiment which is amodification of the earlier relay, the magnetic backstop 28, provides asmall additional holding force on the armature and is the main means ofreducing contact bounce.

This is a non-polarized relay. The small magnets 30 (FIGS. 6, 7, and 8)are positioned so that one has its N-pole, and the other has its S-pole,facing the underside of the armature 12'. The block of magnetic iron 29acts as a magnetic flux carrier so that the magnetic backstop 28effectively constitutes a horseshoe permanent magnet.

The holding force on the armature is due to a magnetic flux path aroundthe horseshoe magnet and across the width of the armature 12. Thismagnetic flux path is substantially at right angles to the main magneticflux path, through the armature which operates the relay. Thus, althoughthe magnetic backstop 23 results in slight increase in the necessaryoperating current, it does not aifect the non-polarity of the relay.

It is not essential tothe invention that the horseshoe magnet used toreduce contact bounce should be in the form of a backstop for thearmature relay, as in the above described embodiment; a separatebackstop might, of course, be used. Also the form of the horseshoemagnet in the above described embodiment is specifically for use in anon-polarized electromagnetic relay. Clearly,

permanent magnets or magnetic backstops of different forms, having onlyone type of magnetic pole acting on the armature, could be used inpolarized electromagnetic relays for reducing contact bounce.

What I claim is:

l. In a non-polarized electromagnetic relay, a magnetic structurecomprising a pair of salient poles, flux generating means associatedwith said structure, a balanced armature positioned between said polesin flux linking relationship therewith and operable between an operatedand unoperated position in response to variations in magnetic flugenerated by said flux generating means traversing the said armature,and magnetic damping apparatus disposed adjacent one end of saidarmature to urge the armature in its unoperated position by a secondmagnetic flux traversing said armature in a direction normal to thedirection of the first said magnetic flux.

2. A non-polarized electromagnetic relay as set forth in claim 1 whereinsaid magnetic damping means comprises a permanent magnet having itspoles positioned adjacent the same end of said armature.

3. A non-polarized electromagnetic relay as set forth in claim 1 whereinthe said magnetic damping means comprises backstop means limiting themovement of said armature in its unoperated position.

4. A non-polarized electromagentic relay as set forth in claim 1 whereinone of said salient poles is flux-linked with an intermediate portion ofsaid armature.

5. A non-polarized electromagnetic relay as set forth in claim 1 whereinthe flux of the magnetic fields generated by said flux generating meansand by said magnetic damping means are substantially independent of eachother.

6. A non-polarized electromagnetic relay as set forth in claim 1 whereinsaid armature includes biasing means urging one end of said armaturefrom its operated position to its unoperated position into flux linkingrelationship with said magnetic damping means.

References Cited by the Examiner UNITED STATES PATENTS 2,915,681 12/59Troy 317 -171 3,013,136 12/61 De Fringue 317-l71 JOHN F. BURNS, PrimaryExaminer. E. JAMES SAX, Examiner.

1. IN A NON-POLARIZED ELECTROMAGNETIC RELAY, A MAGNETIC STRUCTURECOMPRISING A PAIR OF SALIENT POLES, FLUX GENERATING MEANS ASSOCIATEDWITH SAID STRUCTURE, A BALANCED ARMATURE POSITIONED BETWEEN SAID POLESIN FLUX LINKING RELATIONSHIP THEREWITH AND OPERABLE BETWEEN AN OPERATEDAND UNOPERATED POSITION IN RESPONSE TO VARIATIONS IN MAGNETIC FLUXGENERATED BY SAID FLUX GENERATING MEANS TRAVERSING THE SAID ARMATURE,AND MAGNETIC DAMPING APPARATUS DISPOSED ADJACENT ONE END OF SAIDARMATURE TO URGE THE ARMATURE IN ITS UNOPERATED POSITION BY A SECONDMAGNETIC FLUX TRAVERSING SAID ARMATURE IN A DIRECTION NORMAL TO THEDIRECTION OF THE FIRST SAID MAGNETIC FLUX.